Environmental mismatch hypothesis

The environmental mismatch hypothesis posits that many contemporary human health problems — obesity, diabetes, cardiovascular disease, anxiety disorders, and social pathologies — arise because cognitive and physiological mechanisms evolved in one environment (the Pleistocene) are now operating in a radically different one (industrial modernity). The claim is not that humans have stopped evolving but that the rate of cultural and technological change has vastly outpaced the rate of genetic adaptation, producing a systemic lag.

The hypothesis has been invoked to explain everything from the appeal of sugar and fat to the difficulty of maintaining social cohesion in large-scale anonymous societies. Its explanatory power is greatest when specific mechanisms can be identified: the craving for caloric density is a mismatch between foraging appetites and food abundance; the stress response is a mismatch between threat-detection systems evolved for predators and the chronic psychosocial stressors of modernity. Its weakness is that it risks becoming a post-hoc explanation for any modern pathology without generating specific, testable predictions about which mismatches will produce which disorders in which populations. The challenge is to move from storytelling to mechanism.